This invention relates to solids/liquids separators, and more particularly to a two stage clarifier apparatus for separating solids from mixed liquor in a sewage treatment system to produce a clarified effluent.
The effluent from sewage treatment systems is commonly treated to remove solids and to produce a clarified effluent prior to disposal of the effluent, such as by releasing the effluent into the environment. Typical conventional clarifier apparatus devices include filtration devices, e.g. in a fixed bed filtration system such as that described in U.S. Pat. No. 4,008,159 of Besik, and settling basins such as that described in U.S. Pat. No. 4,081,368 of Block et al. In addition, sewage treatment apparatus is disclosed in my prior U.S. Pat. Nos. 4,142,975 and 4,238,338 which includes a quiescent zone associated with the discharge end of the apparatus wherein solids are settled from liquids in the quiescent zone to produce a clarified effluent.
Although each of the foregoing devices have met some degree of success in accomplishing their intended purposes, it has been determined that higher degrees of effluent clarification can be readily and economically obtained in a two stage clarifier apparatus having tank means defining a first quiescent zone, inlet means for supplying mixed liquor from the sewage treatment system to the first quiescent zone, second tank means defining a chamber, baffle means in the chamber for separating the chamber into an aeration zone and a second quiescent zone, first fluid communication means for withdrawing partially clarified effluent from an upper portion of the first quiescent zone and supplying the partially clarified effluent to the aeration zone in the treatment chamber of the second tank means, second fluid communication means providing fluid communication between a lower portion of the aeration zone and a lower portion of the second quiescent zone, and outlet means for withdrawing clarified effluent from an upper portion of the second quiescent zone.